如何在动画开启时更改 CABasicAnimation 的 toValue/fromValue

Question

我正在尝试更改动画为 heartBeatAnimation

的 CABasicAnimation 的 toValue/fromValue 的值

let heartBeatAnimation = CABasicAnimation(keyPath: "transform.scale.xy")
heartBeatAnimation.duration       = 0.75
heartBeatAnimation.repeatCount    = Float.infinity
heartBeatAnimation.autoreverses   = true
heartBeatAnimation.fromValue      = 1.0
heartBeatAnimation.toValue        = 1.15

当动画开启时，我在动画期间获得 transform.scale 的当前值：

let currentValue = someView.layer.presentation()?.value(forKeyPath: "transform.scale")
heartBeatAnimation.fromValue = currentValue
heartBeatAnimation.toValue   = currentValue

在我更改值后，heartBeatAnimation 不会更改其 toValue/fromValue，直到我删除动画然后再次添加！

有什么方法可以在动画播放时实时进行这些更改吗？！

Answer 1

您可以通过将模型层当前比例更新为表示层比例然后读取动画并更新 beginTime 属性使其实时显示，这样动画就好像从未停止过一样.这是一个例子。

import UIKit

class ViewController: UIViewController {


    var scale : CGFloat = 1.2

    var shapeLayer : CAShapeLayer!
    var button : UIButton!

    override func viewDidLoad() {
        super.viewDidLoad()
        //add a shapelayer
        shapeLayer = CAShapeLayer()
        shapeLayer.frame = CGRect(x: 0, y: 0, width: self.view.bounds.width/4, height: self.view.bounds.width/4)
        shapeLayer.position = self.view.center
        shapeLayer.path = drawStarPath(frame: shapeLayer.bounds).cgPath
        let color = UIColor(red: 0.989, green: 1.000, blue: 0.000, alpha: 1.000)
        shapeLayer.fillColor = color.cgColor
        self.view.layer.addSublayer(shapeLayer)


        //button for action
        button = UIButton(frame: CGRect(x: 0, y: 0, width: self.view.bounds.width - 20, height: 50))
        button.center = self.view.center
        button.center.y = self.view.bounds.height - 70
        button.addTarget(self, action: #selector(ViewController.pressed(sender:)), for: .touchUpInside)
        button.setTitle("Animate", for: .normal)
        button.setTitleColor(.blue, for: .normal)

        self.view.addSubview(button)

    }

@objc func pressed(sender:UIButton) {

     var isInterupted = false

        if let presentation = shapeLayer.presentation(){
            if let animScale = presentation.value(forKeyPath: "transform.scale.xy"){
                if let value = animScale as? CGFloat{
                    //set current animation spot
                    shapeLayer.transform = CATransform3DScale(CATransform3DIdentity, value, value, 1)
                    shapeLayer.removeAllAnimations()
                    scale += 0.2
                    isInterupted = true
                    print("The current toValue is \(scale)")

                }
            }
        }


        button.setTitle("Animating...", for: .normal)

        let heartBeatAnimation = CABasicAnimation(keyPath: "transform.scale.xy")
        heartBeatAnimation.duration       = 0.5
        let beginTimeNeeded = (1/scale) * CGFloat(heartBeatAnimation.duration)
        heartBeatAnimation.repeatCount    = .greatestFiniteMagnitude
        heartBeatAnimation.autoreverses   = true
        heartBeatAnimation.fromValue      = 1.0
        heartBeatAnimation.toValue        = scale
        if isInterupted == true{
            heartBeatAnimation.beginTime = CFTimeInterval(beginTimeNeeded)
        }
        heartBeatAnimation.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseInEaseOut)
        shapeLayer.add(heartBeatAnimation, forKey: "beatAnimation")
    }

    func drawStarPath(frame: CGRect = CGRect(x: 0, y: 0, width: 140, height: 140)) ->UIBezierPath{
        //// Star Drawing
        let starPath = UIBezierPath()
        starPath.move(to: CGPoint(x: frame.minX + 0.50000 * frame.width, y: frame.minY + 0.21071 * frame.height))
        starPath.addLine(to: CGPoint(x: frame.minX + 0.60202 * frame.width, y: frame.minY + 0.35958 * frame.height))
        starPath.addLine(to: CGPoint(x: frame.minX + 0.77513 * frame.width, y: frame.minY + 0.41061 * frame.height))
        starPath.addLine(to: CGPoint(x: frame.minX + 0.66508 * frame.width, y: frame.minY + 0.55364 * frame.height))
        starPath.addLine(to: CGPoint(x: frame.minX + 0.67004 * frame.width, y: frame.minY + 0.73404 * frame.height))
        starPath.addLine(to: CGPoint(x: frame.minX + 0.50000 * frame.width, y: frame.minY + 0.67357 * frame.height))
        starPath.addLine(to: CGPoint(x: frame.minX + 0.32996 * frame.width, y: frame.minY + 0.73404 * frame.height))
        starPath.addLine(to: CGPoint(x: frame.minX + 0.33492 * frame.width, y: frame.minY + 0.55364 * frame.height))
        starPath.addLine(to: CGPoint(x: frame.minX + 0.22487 * frame.width, y: frame.minY + 0.41061 * frame.height))
        starPath.addLine(to: CGPoint(x: frame.minX + 0.39798 * frame.width, y: frame.minY + 0.35958 * frame.height))
        return starPath
    }

}

我正在按下按钮为动画添加更多比例。这是结果：

如何在动画开启时更改 CABasicAnimation 的 toValue/fromValue

How can I change toValue/fromValue of CABasicAnimation while the animation is on

ios

animation

swift3

cabasicanimation